The present invention relates to a directional control valve, particularly to a directional control valve which supplies hydraulic fluid from a fluid pump to a power-disconnecting hydraulic clutch of a torque convertor.
A torque convertor transmits power by means of hydraulic fluid. Wherein the torque convertor is installed in a vehicle together with a manual transmission, a power-disconnecting clutch is provided between the turbine of the torque convertor and the main drive shaft extending from the manual transmission. The power-disconnecting clutch engages and disengages a front cover joined to the torque convertor impeller and a power output member connected to the main drive shaft. The power-disconnecting clutch is activated by hydraulic fluid supplied by a hydraulic circuit. Fluid for lubrication of the clutch is also supplied by the hydraulic circuit.
In this kind of power disconnecting clutch, it is particularly necessary to supply lubrication fluid to the clutch wherein a plurality of mutually contacting clutch plates are employed. Japanese Patent Application Laying-Open No. 98757/1989 shows a clutch device structure in which when a piston begins to press a plurality of clutch plates under the agency of hydraulic fluid, the piston also presses washer-type springs located radially inward of the clutch device. As the washer-type springs are compressed, a lubrication-fluid supply opening, which is otherwise closed off by the washer-type springs, is opened, whereby lubrication fluid is supplied to the clutch plates.
Passages in the above-described clutch device through which the lubrication fluid passes are structurally complex, complicating the clutch manufacturing process. Moreover, due to error in the accuracy of assembling washer-type springs, uncertainly arises concerning supply of the lubrication fluid to the clutch plates during engagement.